Difference Between Steady State and Transient Thermal Analysis

The key difference between steady state and transient thermal analysis is that steady state analysis is done at a constant temperature while transient thermal analysis is done at varying temperatures.

Steady state and transient thermal analysis are two processes that involve the study of changes of substances as a function of time.

CONTENTS

1. Overview and Key Difference
2. What is Steady State Thermal Analysis
3. What is Transient Thermal Analysis
4. Side by Side Comparison – Steady State vs Transient Thermal Analysis in Tabular Form
5. Summary

What is Steady State Thermal Analysis?

Steady state thermal analysis is the analysis of changes in the properties of a substance at a constant temperature. First, we should understand what is a steady state as defined in chemistry. Steady state is the stage of a chemical reaction and it has a constant concentration of an intermediate product. If a certain chemical reaction occurs through several steps (elementary steps), we can determine the rate of the reaction using the rate-determining step. And, this step is the slowest step among others. But, when the reaction steps are not recognizable, we cannot recognize the slowest step as well. At such situations, we can consider the intermediate product that has a constant concentration for a short time.

Furthermore, elementary steps of the reaction form intermediate molecules. Intermediates are molecules that are not either reactants or final products but are molecules that form during the progression of a chemical reaction. The short-lived intermediate is formed in the steady-state of the reaction. Moreover, in contrast to an equilibrium state, at steady state, the concentrations of reactants and products change over time (because at the equilibrium, neither the concentration of reactants nor products changes, they keep constant).

Now, let’s go back to steady state thermal analysis. The steady state thermal analysis is the final step of transient thermal analysis. The steady state thermal analysis is important in determining the temperatures, thermal gradients, heat flow rates, heat fluxes, etc. in objects upon the supply of constant heat. The sources of heat we can use for steady state thermal analysis include convection, radiation, and constant temperature boundaries. Furthermore, this type of analysis gives a linear graph when drawn as a function of time.

What is Transient Thermal Analysis?

Transient thermal analysis is the determination of the changes of a substance that occur due to the changes in temperature calculated over a particular time period. That means; this type of analysis deals with the temperatures and other thermal qualities and their variation with time. In this analysis technique, we can determine heat treatment problems, problems associated with nozzles, engine blocks, piping systems, pressure vessels, etc. Usually, if we draw a graph as a function of time, the graph is nonlinear.

What is the Difference Between Steady State and Transient Thermal Analysis?

Steady state and transient thermal analysis are two processes that involve the study of changes of substances as a function of time. The key difference between steady state and transient thermal analysis is that steady state analysis is done at a constant temperature while transient thermal analysis is done at varying temperature. Furthermore, if we express these analysis details on graphs, steady state thermal analysis gives a linear graph whereas transient thermal analysis gives a nonlinear graph.

The below infographic summarizes the difference between steady state and transient thermal analysis.

Summary – Steady State vs Transient Thermal Analysis

Steady state and transient thermal analysis are two processes that involve the study of changes of substances as a function of time. The key difference between steady state and transient thermal analysis is that steady state analysis is done at a constant temperature while transient thermal analysis is done at varying temperature.

Reference:

1. “Chapter 3: Transient Thermal Analysis.” THERMAL: Chapter 3: Transient Thermal Analysis (UP19980818), Available here.

Image Courtesy:

1. “Steady state schematic” Von Indoor-Fanatiker – Eigenes Werk (CC BY-SA 3.0) via Commons Wikimedia